A refrigeration cycle apparatus is known in which a compressor, a condenser, a pressure reducing unit and an evaporator are connected to each other by pipes, and an accumulator and a fusing plug are provided at a low-pressure-side pipe between the evaporator and the compressor (Jpn. Pat. Appln. KOKAI Publication No. 2013-228129).
The fusible plug is provided to prevent the internal temperature and pressure of the accumulator from rising to high values because of an abnormal rise of atmospheric temperature which is caused by, for example, a fire, to thereby prevent the accumulator from being broken. When a detected temperature reaches a predetermined value, the fusible plug fuses to open the low-pressure-side pipe or the accumulator to the atmosphere. As a result, a high-pressure gas in the accumulator flows out therefrom to the outside, thus preventing the accumulator from being broken.
In a heat-pump-type refrigeration cycle apparatus which can perform heating, during heating, frost gradually adheres to a surface of an outdoor heat exchanger functioning as an evaporator, and a heat-exchange efficiency of the outdoor heat exchanger decreases if no countermeasures are taken. In view of this, in the heat-pump-type refrigeration cycle apparatus, if frost adheres to the outdoor heat exchanger, a so-called reverse-cycle defrosting operation is performed. In this defrosting operation, the flowing direction of refrigerant is reversed, and refrigerant discharged from the compressor is directly supplied to the outdoor heat exchanger.
However, if the reverse-cycle defrosting operation is performed, a low-pressure gas refrigerant flows into a pipe in which a high-pressure gas refrigerant flows to increase the temperature of the pipe to a high level. While the low-pressure gas refrigerant is absorbing heat of the pipe having a high temperature, its temperature of the low-pressure gas refrigerant rises to a high temperature. The low-pressure gas refrigerant having a high temperature flows into the low-pressure-side pipe. At this time, heat of the refrigerant flowing into the low-pressure-side pipe is transmitted to the fusible plug. Thus, although the inner pressure of the accumulator is not abnormal, there is a possibility that the fusible plug will fuse.